Wooden ‘plyscrapers’ reinforce the case for use of timber in construction

By E&T editorial staff

Published Wednesday, February 22, 2017

Skyscrapers made from timber are becoming increasingly prevalent as an alternative to traditional concrete and steel constructions.

A 52.8-metre apartment block - dubbed “The Tree” - was recently constructed in Norway and is currently the tallest wooden structure in the world.

Ultra-strong wooden materials are being used in a small but fast-growing market for timber used to build big, urban blocks, extending wood’s uses beyond the houses typical of Alpine villages or suburban America.

Backers of timber towers say they are greener than concrete and steel, whose production emits large amounts of greenhouse gases. Those industries say felling trees harms the environment if it causes loss of forests.

“Steel was the 1800s materials, concrete 1900s. Now we are in the 2000s and it is time for timber,” said Susanne Rudemstan, head of the Swedish Wood Building Council. She said trees must come from properly managed forests to avoid deforestation.

The Tree's interior is supported by thick wooden beams

Records are falling fast in the world of “plyscrapers”, which get their name from the plywood-like laminates glued together to form the wooden beams used to build them.

The Tree (“Treet” in Norwegian), with a roof terrace atop 14 storeys on the waterfront of the port of Bergen, became the world’s tallest wooden apartment block on completion in late 2015, surpassing a building in Melbourne, Australia.

In September, the world title will go to Vancouver, Canada, when students move into a 53-metre, 18-storey residence at the University of British Columbia (UBC).

That building will save an estimated 2,432 tonnes of carbon dioxide compared to other construction materials, the equivalent of taking 500 cars off the road for a year, UBC says.

“It was quick, it was quiet and there wasn’t a mess,” John Metras, managing director for infrastructure development at UBC, said of the construction site.

Elsewhere, construction began last October on an 84-metre wooden tower in Vienna, due for completion next year, while architects are considering even taller blocks, such as a 300-metre “Toothpick” in London.

The cost of building with cross-laminated timber (CLT), one of the main materials, is 10-15 per cent more than with masonry or cement in the main European market, a UN 2015-16 review said, although prices could fall as the industry matures.

The use of CLT often shortens construction times, the review says, because many parts can be pre-fabricated. The frame of the Vancouver high-rise took less than 10 weeks to build, which Metras said was much shorter than for a concrete building.

Exterior of The Tree

In Bergen, The Tree - using wood from sustainable forests - shows that people are ready to live up high with wood, although residents said that family and friends fretted unduly about fire risks.

“We think it’s very fire-safe,” said Soeren Skaar, 24, a psychology student who owns a flat. In a blaze, he said thick wood beams can retain strength better than metal, which can buckle.

Still, some fire detectors have been over-sensitive. “We’ve had a few false fire alarms. The first one was a guy brewing beer in the basement,” said Rolf Einar Vaagheim, 26, an offshore worker who rents an apartment.

Height records are a showcase for what the timber industry hopes will be wider use of wood in construction, while producers of iron ore and steel struggle with low prices.

LafargeHolcim, the world’s biggest cement maker, says plyscrapers are only a marginal threat to an industry dating back to the Romans, who built the vast concrete roof of the Pantheon almost 2,000 years ago.

“Concrete is the most-used building material in the world by far - about 30 billion tonnes (a year). It’s affordable, resilient in time against weather, earthquakes and fire,” said Bernard Mathieu, head of sustainable development at LafargeHolcim.

He also disputed that timber is better for the environment than cement production, which he said accounts for five per cent of world emissions of carbon dioxide, the main greenhouse gas.